Resistance set.



PATENTED JUNE 16, 1903.

E. F. NORTHRUP.

RESISTANCE SET.

APPLICATION FILED MAB. 31 1903.

N0 MODEL.

ERR fncooea UNITED STATES Patented June 16, 1903.

PATENT OFFICE.

EDWIN F. NORTHRUP, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO MORRIS E.LEEDS AND COMPANY, OF PHILADELPHIA, PENNSYLVANIA,

A FIRM.

RESISTANCE SET.

SPECIFICATION forming part Of Letters Patent N0. 731 ,210, dated June16, 1903.

Application filed March 31, 1903. Serial No. 150,392. (No model.)

T0 (6 whom, it may concern:

Be it known that I, EDWIN F. NORTHRUP, a citizen of the United States,residing at Philadelphia, in the county of Philadelphia and State ofPennsylvania, have invented certain new and useful Improvements inResistance Sets, of which the following is a specification.

The principal objects of this invention are to effect an arrangement ofresistances where by a comparatively large number of resistance valuesmay be gotten from a small number of resistances and also to effect anarrangement of connections whereby these values may be obtained inregularly-increasing order byintroducing the resistances between twocontacts or brushes through which current passes to and from saidresistances, and between which brushes and resistances there is relativemovement.

A further object of this invention is to effect an arrangement ofresistances whereby one may expeditiously obtain a series of ratios ofresistance-such, for example, as are required in making a variety oftests with a Wheatstone bridge.

To the above ends this invention consists in the novel combination andarrangement of parts herein described, and particularly pointed out inthe claims. The invention will be more fully described With reference tothe accompanying drawings, in which- Figure 1 is a diagram showing aseries of contact plates, resistances, and electrical connections foreffecting the combining of the resistances in order to give a series ofregularly-increasing values of resistance greater in number than theresistances employed. Fig. 2 is a diagram showing means foraccomplishing the same result with a different combination ofresistances. Fig. 3 is a diagram showing a series of contact-plates,ratio resistance-coils, and connections for varying the ratios. Fig. 4is a conventional diagram of a Wheatstone bridge, and Fig. 5 is adiagram of a 'Wheatstone bridge equipped with resistance sets andratio-coils arranged according to this invention and constituting animproved form of testing set.

It has hitherto been customary in varying electrical resistance in acircuit to connect the terminals of the oircuitto the resistances and toalter the resistance by cutting in or out of the circuit varying amountsof resistance by means of plugs, brushes, or other contact-makers, whichform no part of the terminal connections or only one of the terminals.In the common form of rheostat the brush is usually connected to one ofthe terminals, while the other terminal is permanently secured to theresistancecoils. In

'contradistinction to all such methods the present inventioncontemplates varying the resistance by inserting varying amounts ofresistance between two brushes or other suitable contacts, vrhich aredirect connected to the terminals of the electric circuit. Theresistances are in this case of such values as may be combined to giveregularly-increasing value of resistance greater in number than theresistances employed. These combinations of resistance arepredetermined, and the said resistances are connected up in accordancewith said combinations to a series of contact-plates. The resistance isthen varied by bringing successive combinations of said contact-platesinto engagement with said brushes. 1 have discovered that by giving theresistances certain values and by con meeting them in certainprearranged combinations I may by means of the arrangement ofconnectionsabove referred to get ten regularly increasing values ofresistance with only four resistances.

A specific case embodying the above principle of varying. resistances isshown in Fig. 1, where a I) represent brushes or other suitablecontactnakers adapted to form the terminals of an electrical circuit,into which varying amounts of resistance is to be inserted, 1Q, 2Q, 3.0,and 4!), four resistances having the values, respectively, of one ohm,two ohms, three ohms, and four ohlns, and O, 1, 2, 3, 4, 5, 6, 7, 8, 9,l0, and 11 a series of contact plates or segments, to which the saidresistances are permanently connected in the combinations as shown. Thevariations in resistance may be effected by either moving the brushes ab over the segments or by making the brushes stationary and the segmentsmovable. In most cases the latter would be preferable, for should thebrushes be'made movable they would have to either make a sliding contactwith the terminals ofthe circuit or be provided with flexible leads. Theresistances and contact-plates may be readily mounted together upon asuitable movable support, such as a cylinder or sector, or otherwise.Considering the brushesab stationary and the contact-plates andresistances movable, letitbe required to get successive values ofresistance from zero to nine ohms. For obtaining these valuessuccessively the contacts are moved beneath the brushes in the directionof the arrow. \Vhen the segment 0 comes beneath the brushes, noresistance will be introduced thereby into the circuit, since thissegment acts merely as a connection of inappreciable resistance. Thenext step brings the brushes in contact with segments 0 and l, and thiswill introduce the one-ohm coil into the circuit. For two ohms thecontacts are moved up another step, when the brushes will be broughtinto contact, respectively, with segments 0 and 2, ,introducing thetwo-ohm coil into the circuit and cutting out the one-ohm coil. Forthree ohms the contacts are moved up another step, when the brushes comein contact with segments 3 and 10, connecting the three-ohm coil incircuit and cutting out the two-ohm coil, and by moving the contacts upanother step the brushes are brought into contact with segments Land 10,when the four-ohm coil will be inserted in the circuit and the three-ohmcoil cut out. For five ohms the brushes rest upon segments 5 and 10. Inthis case the current entering by brush a passes through the four-ohmcoil to segment t and thence by wire 12 to segment 0 and through theone-ohm coil, conductor 13 to the segment 5 and negative brush Z),making five ohms of resistance in the circuit. For six ohms the brushesrest upon segments 6 and 10. In this. case the current passes throughthe four-ohm and the two-ohm coils in series and takes the followingcourse: brush a, segment 10, four-ohm resistance, segment 4, conductor12, segment 0, two-011m resistance, segment 2, conductor let, segment 6,to brush 1). Likewise by bringing the segments 7 11, 8 11, and 9 11 incontact successively with the brushes I may obtain in .so many steps thevalues of seven, eight, and nine ohms. For seven ohms the current passesthrough the three and four ohm resistances, for eight ohms through thethree, four, and one ohm resistances, and for nine ohms through thethree, four, and two ohm resistances. Thus it will be seen that a decadeset may be gotten which employs only four coils and in which thesuccessive values are gotten by merely moving step by step a series ofcontact plates or segments beneath a pair of circuit-terminals.

One other combination of four resistances which may be combined to givenine regularlyincreasing values by being successively connected betweentwo terminal contacts is the combination ofoneohm,two ohms,threeohms,and six ohms. This combination of resistances with connections foreffecting the regularly-increasing values is shown in Fig. 2. Thiscombination of resistances necessitates a slight change in thecontact-plates and connections, as will be readily seen from the diagramFig. 2. In this latter case segment 10 is shortened and an extra segment15 inserted between it and segment 11. In Fig. 2 segments 3 and 10 areconnected together, as are segments 6 and 11 and 15 and 0. By moving thecontact plates or segments in Fig. 2 beneath the brushes ct Z), asdescribed relative to Fig. 1., successive values may be obtained fromnaught to nine ohms, inclusive.

While I have shown and mentioned two combinations of resistances havingthe values of one, two, three, and four ohms, and the other values ofone, two, three, and six ohms, obviously by multiplying the values ineach set by any constant, as ten, I may still get the same number ofvalues. For example, I may use the combination 10, 20, 30, and -10 andget ten values from naught to ninety in steps of ten ohms, or by usingthe combination 100, 200, 300, and 400 may get ten values from naught tonine hundred by steps of one hundred ohms, and so on.

In Fig. 3 is shown my improved arrangementfor obtaining a series ofratio values of resistance, where 10,000I).,1,000.0, 1000.,100, and 1!)represent a plurality of ratio resistances or resistance-coils, and 1',2, 3', a, and

'5 a series of contact plates or segments connected to said resistances,as shown. 1 2" 3 4: 5 represent a series of contact plates or segmentssimilar to the series 1' to 5, but arranged in reverse order. Thesegments of the series 1' to 5' are electrically connected tocorresponding segments in the series 1 to 5". The brushes a and b areadapted to make contact successively with the segments 1 to 5 and 1" to5", respectively. For this purpose the said segments may be mounted.upon any suitable moving support and the brushes mounted on a stationarysupport, or the brushes may be movable and the segments stationary, butthe former arrangement is preferred. This arrangement of resistances andconnections (shown in Fig. 3) is designed especially for varying thevalues of the ratio resistances of a \Vheatstonebridgesuch, for example,as the ratio resistances R and R of the IVheatstone bridge, shown inFig. 4, where A represents the known and X the un- A lt X' the point 0,Fig. 3, correspond to the point a of Fig. 4; and let the contact-brushesa b, Fig. 3, correspond to the points of current enknown resistance. Insuch a case trance and exit a b of Fig. 4. Then if it is required thatthe ratios g, shall be f the segments, Fig. 3, are advanced in thedirection of the arrow until the brushes a I) rest, respectively, onsegments 1 and 5". This will introduce into the battery-cin cuit betweenthe brushes rt b and the galvanometer connection 0' the resistance-coils10,000 and 1 in' the same relation as shown in Fig. 4. For a ratio ofone thousand to one the segments of Fig. 3 are moved up until thebrushes or contacts a 0 rest, respectively, upon segments 2 and 5", whenthe 1,000!) and 112 coils will be connected in circuit, as R and R ofFig. 4. Further, if it R 10 is desired that the ratio shall be as thesegments of Fig. 3 are advanced until the brushes a I) rest,respectively, upon segments at and 2", when the 10.0 and lower 1,0000.coils will be connected in circuit. Therefore by advancing the segmentsstep by step beneath the brushes a 1) nine ratio values may be gottenwith the six resistances.

is obtained;

1 000 th th d for e 1r 10 1,000 for For the first step the value for thesecond, %2

1 1 d f t th an or he nin 10,000

for the fourth, for the fifth,

100 h v t e SlXlil],

O the el hth,

Obviously the values thus given the resistances may be varied withoutdeparting from the spirit of the invention.

A testing set comprising a Wheatstone bridge equipped with myimprovedratio and resistance sets is diagrammatically shown in Fig. 5, in whichU, T, H, and TH represent the units, tens, hundreds, and thousandresistances of as many decade sets, constructed as shown in Fig. 1 or 2.R and R represent the ratio resistance-coils, which are arranged asshown in Fig. 3; B, the battery, and G the galvanometer, and a, b c dpoints corresponding to similarly-lettered portions of the bridge shownin Fig. 4. Each decade set of resistances U to TH contains only fourcoils, from each of which may be derived ten values, as fully describedwith relation to Figs. 1 and 2. In using the testing set the unknownresistance is connected between the terminals Y Z, the ratio-coils R andR adjusted according to the method described with reference to Fig. 3,and the resistances U to TH varied by the method described with relationto Figs. 1 and 2 until a balance is obtained, when the values ofresistance may be read off from the position of the brushes on segmentsof the sets U to TH.

While the application of my method of comfor the seventh, for

bining resistances to the Wheatstone bridge, as described, is quite auseful one, still I do not wish to be understood as confining myinvention to such an application, as there are many other uses to whichit may be put.

What I claim as my invention is l. The combination with a plurality ofelectrical resistances, of a plurality of contactpieces of greaternumber than said resistances and connected in prearranged combinationsto said resistances so as to give a series of values of resistancegreater in number than the resistances employed, and a pair of terminalcontacts adapted to make contact successively with combinations of saidcontact-pieces in the obtaining ofsaid values.

2. The combination with a plurality of electrical resistances, of adouble row of contactpieces greater in number than said resistances andconnected to said resistances in prearranged combinations so as to givea series of regularly increasing values of resistance greater in numberthan the said resistances employed, and a pair of contact-makers formingthe terminals by which the electric current is led into and out of saidcontacts and resistances, said contact-makers being adapted to makecontact with combinations of said contact-pieces successively inobtaining said values.

3. A decade resistance set, having four re; sistances, a plurality ofcontact-pieces greater in number than said resistances connectedtogether and to said resistances so as to give ten regularly-increasingvalues of resistance, and a pair of contact-makers forming the terminalsby which current is led to and from said contact-pieces and resistances,said contact-makers being adapted to make contact with combinations ofsaid contact-pieces successively in obtaining said values.

4. The combination with a plurality of electrical resistances, of aplurality of contactpieces of greater number than said resistances andconnected together and to said resistances in prearranged combinationsso as to give a series of ratio values of resistance greater in numberthan the resistances employed, and a pairof terminal contacts adapted tomake contact successively with combinations of said contact-pieces inthe obtaining of said values. 1

5. The combination witha plurality of electrical resistances, of adouble row of contactpieces greater in number than said resistances andconnected together and to said resistances in prearranged order so as togive a series of ratio values of resistance, and a pair of'contact-makers forming the terminals by which the electric current isled into and out of said contacts and resistances, said contact-makersbeing adapted to make contact with combinations of said contact-piecessuccessively in obtaining said values.

6. In a Wheatstone bridge, the combination with a plurality of pairs ofterminal contacts connected in series in the arm of the bridgecontaining the known resistance, of a pinrality 0f decade resistancesets each provided With a double row of contact-pieces and resistancesof lesser number than said contactpieces con n ected thereto in prearran ged combinations, one double row of said contactpieces being providedfor each pair of said terminal contacts and adapted to make contactsuccessively with said terminal contacts 10 in the obtaining of theresistance values.

In testimony whereof I affix my signature in presence of two Witnesses.

EDWIN F. NORTHRUP.

lVitnesses:

-FRANK G. GRIER,

HARRY W. RAUMEL.

